Various processes are disclosed in the art for producing a variety of substituted ethanol amines. For example, U.S. Pat. No. 2,400,913 describes a process for producing various heterocyclic tertiary-amino alcohol compounds. Among the heterocyclic tertiary-amine derivatives disclosed in the '913 patent are furyl tertiary amino alcohols. The compounds of the '913 patent are produced by reacting acyl halide derivatives of the heterocyclic compounds, including furan, with a diazoalkane to yield the corresponding diketone. The diketone is treated with a hydrogen halide to form the .alpha.-halogeno ketones, which, in turn are reacted with secondary amines to yield the corresponding .alpha.-tertiary amino ketones. Those ketones are then reduced to the corresponding alcohol. While the reduction may be carried out with catalytically-activated hydrogen, in the specific case of compounds in the furan series, the reduction is stated to be more advantageously carried out with an oxidizable metal alkoxide, e.g., aluminum isopropoxide, magnesium ethoxide, and the like.
U.S. Patent 2,547,712 describes a process for producing certain 1-[2-furyl]-2-aminopropane diols. In a more relevant disclosure, in Example 2 of the '712 patent, the compound 2-furyl aminomethyl ketone hydrochloride is produced by reacting a 2-furyl bromomethyl ketone hexamethylene tetraamine complex with HCl. In the next step the 2-furyl aminomethyl ketone is added to a mixture of glacial acetic acid and acetic anhydride to which is then added sodium acetate. The product of that reaction is 2-furyl acetamidomethyl ketone, which is reacted with formalin, sodium bicarbonate and methanol to form 2-furyl-.alpha.-acetamido-.beta.-hydroxyethyl ketone. This product was then reduced to the corresponding diol with aluminum isopropoxide (the catalyst of the '913 patent) in isopropanol.
U.S. Pat. No. 4,072,760 discloses another process for producing phenyl-ethanolamines. In one scheme (Column 17) a ketone of a substituted phenyl tertiary amino hydrochloride salt is reduced with a Pd/C catalyst in methanol to the corresponding alcohol. This compound is used to prepare the corresponding compounds of Formula II in '760, which are used to prepare the final products (Formula I) of that patent.
Although it is known to chlorinate methyl ketones, the chlorination of furan derivatives (as in a preliminary step to making chloroacetyl furan as used in the process herein), is a special case. Thus, furan derivatives show extreme susceptibility to acids (Elderfield, Heterocyclic Compounds, J. Wiley and Sons, 1950, pages 161, 170). The HCl co-produced in a chlorination would be expected to decompose the furan ring. This is indicated by the only known process for preparing 2-chloroacetyl furan which is a cumbersome, dangerous synthesis using diazomethane. Election-withdrawing groups, such as NO.sub.2, decrease the sensitivity to acids.
In the preparation of hydrochloride salts of furanamino ketone, by the known Delapine reaction, bromo derivatives are generally used. Accordingly, in the present process, it was found that a tetrabutylammonium bromide catalyst was necessary to catalyze the reaction of 2-chloroacetylfuran with hexamethylenetetraamine to produce the corresponding hydrochloride salt.
Further, the hydrogenation of furan derivatives is not always straight-forward. Elderfield reported that often ring reduction or cleavage occurs. The only reductions in this area are of disubstituted amines only and the reduction is done with an oxidizable metal alkoxide, e.g., aluminum alkoxide, as used in the '913 and '712 patents; such reaction was found not to be operable for a primary amine derivative as herein, but resulted in decomposition.
It is an object of this invention to provide an improved, more efficient and economical process for producing heterocyclic ethanol amines, especially 2-(2furyl)ethanol amine.
The products of this invention are useful as starting materials to produce 5-heterocyclic-substituted oxazolidine compounds, which are useful as antidotes (or "safeners", "antagonistics" or "protectants") to reduce or eliminate the phytotoxicity of herbicides against crop plants, e.g., corn, soybeans, etc. Those said antidotal compounds are publicly known from European Patent Application No. 304,409, published Feb. 22, 1989, and South African Patent No. 5997, issued June 28, 1989.